Multistage centrifugal compressor



Nov. 4, 1969 F. K. KUNDERMAN MULTISTAGE CENTRIFUGAL COMPRESSOR Filed sept. 18, 1967 3 Sheets-Sheet 1 1 N v E N T 0 R Fez-0 K Kala/0594M Q/EQM ATTOQA/EY Nov. 4, 1969 F. K. KUNDERMAN 3,476,485

MULTISTAGE CENTRIFUGAL COMPRESSOR Filed Sept. 18, 1967 3 Sheets-Sheet 2 INVEN TOR. F250 4 KU/VOEGMA/V N 1969 F. K. KUNDERMAN MULTISTAGE CENTRIFUGAL COMPRESSOR 5 Sheets-Sheet 3 Filed Sept. 18, 1967 ATTOIQA/E-Y United States Patent Ofiice 3,476,485 Patented Nov. 4, 1969 US. Cl. 415-66 12 claims ABSTRACT OF THE DISCLOSURE A three stage centrifugal compressor includes a base having two intercooler chambers and two separator chambers defining interstage flow paths, the intercooler chambers communicating with separate openings in a top wall of the base. A cover plate for closing these openings has formed integrally therewith the compressor gearcase volutes for the three stages, the volute diffusers for the first two stages, extending vertically downward and opening to the underside of the cover plate. Two intercoolers, which define vertical fines, are secured to the underside of the cover plate communicating respectively with the volute diffusers for the first two stages. The intercoolers are received in the respective intercooler chambers. Each of the intercooler chambers communicates with a respective separator chamber which includes a large area moisture separator accommodating upward air flow; and conduits communicate the upper portion of each separator chamber with the inlet for the succeeding stage. The first stage impeller is mounted on one shaft, the second and third stage impellers are mounted on a common shaft parallel with the first shaft, both shafts carrying pinions engaged by a drive gear mounted on a third parallel shaft adapted to be coupled to a driving motor.

BACKGROUND OF THE INVENTION An object of this invention is to provide an efiicient three stage centrifugal compressor capable of providing plant air pressure at 100, 110, and 125 p.s.i.g. An accompanying object is to provide such a compressor which is compact and occupies a minimum fioor space. In order to achieve the desired pressures in a machine of this type, careful attention must be given to the design of the air flow paths to eliminate any unnecessary restrictions to air flow between the compressor stages. Further, for good efiiciency, it is necessary to cool the air between the compressor stages; and it is desirable that the air cooling devices be arranged to present minimum restriction to air flow.

SUMMARY OF THE INVENTION According to the invention, the base for the compresor unit includes large area intercooler chambers and moisture separator chambers which define in part the interstage flow paths. The volutes for all but the last stage, at least, are formed integrally with a cover plate for the compressor base, these volutes being disposed on the upper'side of the cover plate and the volute diffusers extending vertically downwardly opening to the underside of the cover plate, to discharge air directly downwardly into the intercooler chambers of the base. The intercooling devices have housings defining vertical conduits which are rigidly attached directly to the underside of the base plate whereby the air flow from the volutes is directed downwardly through the cooling devices into the intercooler chambers. Large area openings communicate the intercooler chambers with the separator chambers; and the air is directed from .the separator chambers to the inlet of the succeeding stage through short length con- I duits having a minimum of turns.

BRIEF DESCRIPTION OF THE DRAWING The invention is diagramatically illustrated in the accompanying drawings, in which:

FIG. 1 is a plan view of the compressor;

FIG. 2 is an elevation view of the compressor of FIG. 1, partially broken away to show internal structure;

FIG. 3 is a fragmentary plan view of the compressor of FIG. 1 with the gearcase cover removed;

FIG. 4 is a view taken along the line 4-4 of FIG. 2, the reference plane being the upper surface of the compressor base; and

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIGS. 1, 2, and 4 of the drawing, a preferred form of compressor according to the present invention includes a hollow base member 11, which may be a casting, which includes a portion 11a defining the base for the compressar assembly and a portion 11b which may define a base for a drive motor (not shown). The portion 11b is integral with the portion 11a; and the portion 11b is only partially shown in the drawings. Both base portions include suitable feet members 12 for supporting the base on a suitable concrete pad or other support. As viewed from the top, the compressor base portion 11a is generally circular; and this portion is divided into four chambers which define flow paths between the compressor stages as will be described. As best seen in FIG. 4, there are provided in the base 11a two intercooler chambers 13 and 14 which are generally rectangular in section as viewed from the top, and adjoin each other being separated by a wall 15. These chambers are open at the top of the base 110, the edges of the openings being defined by a commo edge surface 16, lying in a horizontal plane and defining a mating surface for a closure member to be described.

As viewed in the drawings, the left sides of the intercooler chambers 13 and 14 are defined by a vertical wall 19 which separates the intercooler chambers from a first separator chamber 20. As viewed from the top, this chamber has the shape of the segment of a circle and extends along one side of the base adjoining both of the chambers 13 and 14. As best seen in FIGS. 2 and 5, an opening 21 is provided in the wall 19 communicating the intercooler chamber 13 and the separator chamber 20. This opening 21 is in the lower half of the wall only, so that the air How will be from the lower portion of the intercooler chamber 13 into the lower portion of the separator chamber 20, as will be more fully described subsequently.

Similarly, the right sides of the intercooler chambers 13 and 14, as viewed in the drawings, are defined by a vertical wall 22 which separates these chambers from a second separator chamber 23, which is located on the opposite side of the base 11a adjacent to the portion 11b and also has the shape of the segment of a circle as viewed from the top. The separator chamber 23 is communicated with the intercooler chamber 14 by means of an opening 24 in the wall 22. This opening 24 is similar to the opening 21 in that it exists only in the lower half of the wall 22 to provide for flow of air from the lower portion of the intercooler chamber 14 into the lower portion of the separator chamber 23.

The compressor assembly includes a base plate 27 which is supported by the edge surface 16 of the base 11a and is secured thereto with suitable sealing. Formed integrally with the base plate 27 are the volutes and associated diffusers for the three compressor stages, and the gearcase which houses the gears and shafts for driving the impellers of the three compressor stages. As best seen in FIGS. 1 and 2, these several elements of the compressor assembly are the first stage volute 28 and diffuser 29, the second stage volute 30 and diffuser 31, and the third stage volute 32 and diffuser 33 which includes a flange 34 to which may be attached a suitable discharge conduit (not shown). As best seen in FIG. 3, the gearcase 35 houses and supports the gears and associated structure for the three compressor stages.

The internal structure of the several compressor stages are not shown in the drawings; and these include impellers of generally conventional design. Referring particularly to FIG. 3, the first stage impeller is fixed to a shaft 38 rotatably supported in suitable bearings 39 in the gearcase 35. Formed integrally with the shaft 38, between the bearings 39, is a pinion 40 by means of which the shaft is rotated. The second and third stage impellers are mounted at opposite ends of a shaft 41 disposed parallel to shaft 38 and rotatably supported in suitable bearings 42 at the opposite end of the gearcase 35. The shaft 41 also includes an integral pinion 43 located between the two journal portions. A drive shaft 44 for the compressor assembly is rotatably supported intermediate the shafts 38 and 41 in suitable bearings 45. The drive shaft 44 is adapted to be directly coupled to a drive motor, such as an electric motor; and the shaft 44 carries a relatively large drive gear 46 which meshes with the pinions 40 and 43 to drive the respective impeller shafts at the desired rate of rotation. A gearcase cover 47 encloses the above described gear and shaft assembly.

Each of the compressor stage structures includes a shroud for the volute which includes an inlet nozzle having means for securing an inlet conduit to the stage structure. The first stage volute 28 includes such a shroud 49 providing an inlet nozzle 50 including a flange for the purpose of attaching the inlet conduit to the compressor. A second stage volute 30 includes a shroud 51 with a coupling 52 secured to the inlet nozzle; and the third stage volute 32 includes a shroud 53 and a coupling 54 secured to the inlet nozzle.

As best seen in FIGS. 2 and 4, the portion of the base 11a enclosing the separator chamber 20 is provided with a boss 57 defining an upwardly extending pipe opening communicating with the chamber. The boss is provided with a suitable flange 58 to which is secured a right-angle conduit 59, which connects the separator chamber 20 with the inlet nozzle for the second stage compressor. Similarly, the base 11a is provided with a boss 60 extending upwardly from the base portion defining the separator chamber 23 and defining a pipe opening. The boss 60 is provided with a flange 61; and a right-angle conduit 62 is secured between the flange 61 and the coupling 54 for the third stage inlet nozzle. In this manner, the upper portion of the separator chamber 23 is communicated with the third stage inlet.

Also, as best seen in FIGS. 2 and 4, a pair of intercoolers 65 and 66 are secured to the gearcase base plate 27 and disposed to be received, respectively, within the intercooler chambers 13 and 14. As viewed from the top, these intercoolers are square in section and define a square conduit providing for vertical flow of air downwardly from the first and second compressor stages into the respective intercooler chambers. The intercooler walls are provided with an upper peripheral flange, by means of which the intercoolers are secured, by means of bolting for example, in sealing relation to the underside of the gearcase base plate 27. The intercooler 65 is secured to the base plate and suitably sealed thereto to communicate with the opening from the first stage volute diffuser 29. Accordingly, the discharge air from the first stage is directed vertically downward through the diffuser and directly through the intercooler. Similarly, the intercooler 66 is secured to the base plate and suitably sealed thereto to communicate with the opening from the second stage volute diffuser 31. Accordingly, the discharge air from the second stage is directed vertically downward through the diffuser and directly through the intercooler. The intercoolers may include a plurality of coils for the flow of water to provide the cooling of the air flowing therethrough. As seen in FIG. 2., the intercoolers extend downwardly, within the respective intercooler chambers to a point below mid-depth so that the cooled air is discharged into the lower portions of the respective intercooler chambers.

Referring now to the separator chamber 20, this chamber includes a moisture separator 69 which consists of a mat of stainless steel wire mesh. As viewed from the top, this mat has a shape of the segment of a circle which conforms generally to the shape of the separator chamber 20; and the mat has a substantial thickness. As best seen in FIG. 2, the walls of the separator chamber 20 are provided with a groove 70 disposed in a horizontal plane positioned about midway between the upper and lower extremities of the chamber. This groove defines a support chamber in the shape of the segment of a circle; and the moisture separator 69 is dimensioned to be received and supported within this support chamber. For the purpose of supporting the wire mesh separator within the groove 70, a suitable frame may be provided. The separator 69 is positioned relative to the opening 21 in the wall 19, so that the air flowing into the separator chamber from the intercooler chamber 13 will necessarily enter the lower portion of the separator chamber and flow upwardly through the separator. Similarly, an identical moisture separator 71 is provided within the separator chamber 23, and is supported in a corresponding manner relative to the opening 24 in the wall 22. As indicated, the flow of air through the moisture separators is upward from the lower portion of the respective separator chambers to the upper portion; and the separator area presented to the flowing air is large so that the velocity through the separator is relatively small. The separated moisture drops to the bottom of the base 11 where it is collected by means of suitable traps.

In operation, the drive shaft 44 is driven in a counterclockwise direction, as viewed from the left end of the compressor as presented in the attached drawings; and therefore the impellers of the three compressor stages are rotated in a clockwise direction as viewed from the same vantage point. Inlet air to the compressor enters through the first stage nozzle 50; and the air compressed in the first stage is directed by the first stage volute 28 downwardly through the volute diffuser 29 and directly through the intercooler 65 mounted directly beneath the diffuser 29. Some of the heat of compression is removed from the air as it passes through the intercooler 65 flowing into the lower portion of the intercooler chamber 13. The air then flows from the lower portion of the intercooler chamber 13 through the opening 21 of the wall 19 into the lower portion of the separator chamber 20. This air may then flow laterally through the entire lateral expanse of the separator chamber, being exposed to the substantial surface of the moisture separator 69, the air then flowing upwardly through the separator to the upper portion of the separator chamber 20.

From the separator chamber 20, the air flows upwardly through the right-angle conduit 59 into the nozzle of the second compressor stage, defined by the volute 30 and shroud 51. Since the second stage impeller is mounted on a pinion shaft spaced from that of the first stage impeller, the diffuser portion 31 of the second stage volute 30 is also directed vertically downward so that the air compressed in the second stage also flows vertically downward and directly into the second intercooler 66 which is secured directly beneath this second stage diffuser. Again, the heat of compression is removed from the air in the intercooler 66; and this air is discharged to the lower portion of the intercooler chamber 14 from whence it flows through the opening 24 in the wall 22 into the lower portion of the separator chamber 23. Again the air may flow laterally within the separator chamber 23 to be exposed to the substantial area of the second moisture separator 71, the air flowing at low velocity upwardly through the separator to the upper portion of the chamber 23. a

From the separator chamber 23, the air flows upwardly through the right angle conduit 62 into the nozzle of the third compressor stage, defined by the volute 32 and shroud 53. The air from the third stage is, of course, discharged through the third stage diffuser 33 to a discharge line connected to the flange 34.

An important feature of the compressor, according to the invention, is that the compressor volutes of the several compressor stages are integral with the cover plate for the compressor base and are supported thereby, and that the intercoolers are rigidly mounted directly to the same cover plate, thereby eliminating the need for any expansion joints between these components of the compressor assembly. Another important feature is that the diffuser portions of the volutes for the compressor stages, except the final stage, are directly verticallydownward and in line with associated intercoolers whereby the flow of compressed air through the diffusers and intercoolers is essentially in a straight line. Further, the overall arrangement of the compressor assembly is such that smooth flow of air through the assembly is provided with a minimum of turns and restrictions to flow.

A further feature is that the intercoolers are bolted directly to the base plate and sealed thereto, communicaing directly with the diffuser portions of the volutes..T-his arrangement obviates leakage and bypassing of the heated air around the intercoolers. A small amount of such leakage results in a significant reduction of compressor elficiency.

Still another feature is the arrangement whereby the air flowing from the intercoolers is turned substantially 180 before passing through the moisture separators. With this arrangement, much of the moisture is separated from the cooled air before the air passes through the separators, resulting in improved efilciency of moisture separation.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A three stage centrifugal compressor comprising a base having chambers defining flow paths between the compressor stages; means defining two separate inter-cooler chambers communicating with openings in an upper horizontal wall of said base;

a cover plate for closing said openings; said cover plate having volutes for at least the first two compressor stages for-med unitary therewith, the diffuser portions of said volutes opening to the under side of said cover plate to direct compressed gas vertically downward into said intercooler chambers;

a pair of gas cooling devices sealingly attached to the underside of said cover plate to extend into respective inter-cooler chambers; said cooling devices communicating directly with respective volute diffuser portions of the first two compressor stages, and deifining vertical conduits for the flow of gas from said volutes into respective intercooler chambers; and

passage means communicating each of said intercooler chambers with the inlet of the succeeding compressor stage.

2. A compressor as set forth in claim 1 wherein the impeller for the first compressor stage is mounted on a first shaft; and the impeller for said second compressor stage is mounted on a second shaft parallel to said first shaft and spaced laterally therefrom.

3. A compressor as set forth in claim 2 wherein the impeller for said third compressor stage is mounted on said second shaft; said second and third stage impellers being mounted at opposite ends of said second shaft.

4. A compressor as set forth in claim 2 wherein said shafts are rotatably supported in a gearcase formed integrally with said cover plate.

5. A three stage centrifugal compressor comprising a base having chambers defining flow paths between the compressor stages; means defining two separate intercooler chambers communicating with openings in an upper horizontal wall of said base;

a cover plate for closing said openings; said cover plate having volutes for at least the first two compressor stages formed unitary therewith, the diffuser portions of said volutes communicating with openings in said cover plate to direct compressed gas vertically downward into said intercooler chambers;

a pair of gas cooling devices mounted sealingly on the underside of said cover plate to extend into respective intercooler chambers; said cooling devices communicating directly with respective volute diffuser portions of the first two compressor stages, and defining vertical conduits for the flow of gas from said volutes into respective intercooler chambers;

means in said base defining two separate separator chambers; a moisture separator supported in each of said separator chambers to define upper and lower portions of said chambers;

passageways communicating the lower portion of each of said intercooler chambers with the lower portion of a respective one of said separator chambers, whereby the gas flowing from said intercooler chambers flows upwardly through said moisture separators; and

conduit means communicating the upper portions of each of said separator chambers with the inlet of the succeeding compressor stage; said passageways, said separator chambers and said conduit means defining said passage means.

6. A compressor as set forth in claim 5 wherein each of said conduit means comprises a right angle conduit including a vertical portion communicating with the respective separator chamber and a horizontal portion communicating with the inlet of the respective succeeding compressor stage.

7. A multistage centrifugal compressor comprising a base having chambers defining flow paths between the compressor stages; means defining at least one separate intercooler chambers communicating with openings in an upper horizontal wall of said base;

a cover plate for closing said openings; said cover plate having volutes for at least. one compressor stage formed unitary therewith, said volutes having diffuser portions opening to the under side of said cover plate to direct compressed gas vertically downward into respective intercooler chambers;

at least one gas cooling device sealingly attached to the underside of said cover plate to extend into respective intercooler chambers; said cooling devices communicating directly with volute diffuser portions of respective compressor stages, and defining vertical conduits for the flow of gas :from said volutes into respective intercooler chambers; and

passage means communicating each of said intercooler chambers with the inlet of the succeeding compressor stage.

8. A compressor as set forth in claim 7 wherein the impeller for the first compressor stage is mounted on a first shaft; and the impeller for the second compressor stage is mounted on a second shaft parallel to said first shaft and spaced laterally therefrom.

9. A compressor as set forth in claim 8 wherein the impeller for the third compressor stage is mounted on said second shaft; said second and third stage impellers being mounted at opposite ends of said second shaft.

10. A compressor as set forth in claim 8 wherein said impeller shafts are rotatably supported in a gearcase formed integrally with said cover plate.

11. A base having chambers defining flow paths between the compressor stages; means defining at least one separate intercooler chambers communicating with openings in an upper horizontal wall of said base;

a cover plate for closing said openings; said cover plate having volutes from one or more compressor stages formed unitary therewith, said volutes having diffuser portions communicating with openings in said cover plate to direct compressed gas vertically downward into respective intercooler chambers;

at least one gas cooling devices mounted sealingly on the underside of said cover plate to extend into respective intercooler chambers; said cooling devices communicating directly with volute diffuser portions of respective compressor stages, and defining vertical conduits for the flow of gas from said volutes into respective intercooler chambers;

means in said base defining a plurality of separate separator chambers; a moisture separator supported in each of said separator chambers to define upper and lower portions of said chambers;

passageways communicating the lower portions of each of said intercooler chambers with the lower portion of a respective one of said separator chambers, whereby the gas flowing from said intercooler chambers flows upwardly through said moisture separators; and

conduit means communicating the upper portions of each of said separator chambers with the inlet of the succeeding compressor stage; said passageways, said separator chambers, and said conduit means defining said passage means.

12. A compressor as set forth in claim 8 including pinions nonrotatably fixed to said first and second shafts; and a common drive gear engaging said pinions to rotate said shafts.

References Cited UNITED STATES PATENTS 3,001,692 9/1961 Schierl 230130 3,424,372 1/ 1969 Blattner et a1. 230209 FOREIGN PATENTS 909,853 4/ 1954 Germany.

43,877 8/1938 Netherlands. 102,821 1/ 1924 Switzerland.

HENRY F. RADUAZO, Primary Examiner U.S. Cl. X.R. 

